[Improvement] Implement customer group grid on ui component

app/code/Magento/Customer/Model/ResourceModel/Group/Collection.php

@@ -12,6 +12,11 @@
  */
 class Collection extends \Magento\Framework\Model\ResourceModel\Db\Collection\AbstractCollection
 {
+    /**
+     * @var string
+     */
+    protected $_idFieldName = 'customer_group_id';
+
     /**
      * Resource initialization
      *

app/code/Magento/Customer/Model/ResourceModel/Group/Grid/Collection.php

@@ -7,8 +7,62 @@
  */
 namespace Magento\Customer\Model\ResourceModel\Group\Grid;
 
-class Collection extends \Magento\Customer\Model\ResourceModel\Group\Collection
+use Magento\Customer\Model\ResourceModel\Group\Collection as GroupCollection;
+use Magento\Framework\Api\Search\SearchResultInterface;
+use Magento\Framework\Search\AggregationInterface;
+
+/**
+ * Collection for displaying grid of customer groups
+ */
+class Collection extends GroupCollection implements SearchResultInterface
 {
+    /**
+     * @var AggregationInterface
+     */
+    protected $aggregations;
+
+    /**
+     * @param \Magento\Framework\Data\Collection\EntityFactoryInterface $entityFactory
+     * @param \Psr\Log\LoggerInterface $logger
+     * @param \Magento\Framework\Data\Collection\Db\FetchStrategyInterface $fetchStrategy
+     * @param \Magento\Framework\Event\ManagerInterface $eventManager
+     * @param string $mainTable
+     * @param string $eventPrefix
+     * @param string $eventObject
+     * @param string $resourceModel
+     * @param string $model
+     * @param \Magento\Framework\DB\Adapter\AdapterInterface|string|null $connection
+     * @param \Magento\Framework\Model\ResourceModel\Db\AbstractDb $resource
+     *
+     * @SuppressWarnings(PHPMD.ExcessiveParameterList)
+     */
+    public function __construct(
+        \Magento\Framework\Data\Collection\EntityFactoryInterface $entityFactory,
+        \Psr\Log\LoggerInterface $logger,
+        \Magento\Framework\Data\Collection\Db\FetchStrategyInterface $fetchStrategy,
+        \Magento\Framework\Event\ManagerInterface $eventManager,
+        $mainTable,
+        $eventPrefix,
+        $eventObject,
+        $resourceModel,
+        $model = \Magento\Framework\View\Element\UiComponent\DataProvider\Document::class,
+        $connection = null,
+        \Magento\Framework\Model\ResourceModel\Db\AbstractDb $resource = null
+    ) {
+        parent::__construct(
+            $entityFactory,
+            $logger,
+            $fetchStrategy,
+            $eventManager,
+            $connection,
+            $resource
+        );
+        $this->_eventPrefix = $eventPrefix;
+        $this->_eventObject = $eventObject;
+        $this->_init($model, $resourceModel);
+        $this->setMainTable($mainTable);
+    }
+
     /**
      * Resource initialization
      * @return $this
@@ -19,4 +73,78 @@ protected function _initSelect()
         $this->addTaxClass();
         return $this;
     }
+
+    /**
+     * @return AggregationInterface
+     */
+    public function getAggregations()
+    {
+        return $this->aggregations;
+    }
+
+    /**
+     * @param AggregationInterface $aggregations
+     * @return $this
+     */
+    public function setAggregations($aggregations)
+    {
+        $this->aggregations = $aggregations;
+        return $this;
+    }
+
+    /**
+     * Get search criteria.
+     *
+     * @return \Magento\Framework\Api\SearchCriteriaInterface|null
+     */
+    public function getSearchCriteria()
+    {
+        return null;
+    }
+
+    /**
+     * Set search criteria.
+     *
+     * @param \Magento\Framework\Api\SearchCriteriaInterface $searchCriteria
+     * @return $this
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function setSearchCriteria(\Magento\Framework\Api\SearchCriteriaInterface $searchCriteria = null)
+    {
+        return $this;
+    }
+
+    /**
+     * Get total count.
+     *
+     * @return int
+     */
+    public function getTotalCount()
+    {
+        return $this->getSize();
+    }
+
+    /**
+     * Set total count.
+     *
+     * @param int $totalCount
+     * @return $this
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function setTotalCount($totalCount)
+    {
+        return $this;
+    }
+
+    /**
+     * Set items list.
+     *
+     * @param \Magento\Framework\Api\ExtensibleDataInterface[] $items
+     * @return $this
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function setItems(array $items = null)
+    {
+        return $this;
+    }
 }

app/code/Magento/Customer/Test/Unit/Model/ResourceModel/Group/Grid/CollectionTest.php

@@ -0,0 +1,136 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+declare(strict_types=1);
+
+namespace Magento\Customer\Test\Unit\Model\ResourceModel\Group\Grid;
+
+use Magento\Customer\Model\ResourceModel\Group\Grid\Collection;
+use Magento\Framework\Api\Search\AggregationInterface;
+use Magento\Framework\Data\Collection\Db\FetchStrategyInterface;
+use Magento\Framework\Data\Collection\EntityFactoryInterface;
+use Magento\Framework\DB\Adapter\AdapterInterface;
+use Magento\Framework\Event\ManagerInterface;
+use Magento\Framework\Model\ResourceModel\Db\AbstractDb;
+use Magento\Framework\TestFramework\Unit\Helper\ObjectManager;
+use Psr\Log\LoggerInterface;
+use Magento\Framework\DB\Select;
+
+/**
+ * CollectionTest contains unit tests for \Magento\Customer\Model\ResourceModel\Group\Grid\Collection class
+ * @SuppressWarnings(PHPMD.CouplingBetweenObjects)
+ */
+class CollectionTest extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @var EntityFactoryInterface|\PHPUnit_Framework_MockObject_MockObject
+     */
+    protected $entityFactoryMock;
+
+    /**
+     * @var LoggerInterface|\PHPUnit_Framework_MockObject_MockObject
+     */
+    protected $loggerMock;
+
+    /**
+     * @var FetchStrategyInterface|\PHPUnit_Framework_MockObject_MockObject
+     */
+    protected $fetchStrategyMock;
+
+    /**
+     * @var ManagerInterface|\PHPUnit_Framework_MockObject_MockObject
+     */
+    protected $eventManagerMock;
+
+    /**
+     * @var AdapterInterface|\PHPUnit_Framework_MockObject_MockObject
+     */
+    protected $connectionMock;
+
+    /**
+     * @var AbstractDb|\PHPUnit_Framework_MockObject_MockObject
+     */
+    protected $resourceMock;
+
+    /**
+     * @var AggregationInterface|\PHPUnit_Framework_MockObject_MockObject
+     */
+    protected $aggregationsMock;
+
+    /**
+     * @var Select
+     */
+    protected $selectMock;
+
+    /**
+     * @var Collection
+     */
+    protected $model;
+
+    /**
+     * SetUp method
+     *
+     * @return void
+     */
+    protected function setUp()
+    {
+        $this->entityFactoryMock = $this->getMockBuilder(EntityFactoryInterface::class)
+            ->getMockForAbstractClass();
+        $this->loggerMock = $this->getMockBuilder(LoggerInterface::class)
+            ->getMockForAbstractClass();
+        $this->fetchStrategyMock = $this->getMockBuilder(FetchStrategyInterface::class)
+            ->getMockForAbstractClass();
+        $this->eventManagerMock = $this->getMockBuilder(ManagerInterface::class)
+            ->getMockForAbstractClass();
+        $this->resourceMock = $this->getMockBuilder(AbstractDb::class)
+            ->disableOriginalConstructor()
+            ->getMock();
+        $this->aggregationsMock = $this->getMockBuilder(AggregationInterface::class)
+            ->getMockForAbstractClass();
+        $this->connectionMock = $this->getMockBuilder(AdapterInterface::class)
+            ->getMockForAbstractClass();
+        $this->selectMock = $this->getMockBuilder(Select::class)
+            ->disableOriginalConstructor()
+            ->getMock();
+
+        $this->resourceMock->expects($this->any())
+            ->method('getConnection')
+            ->willReturn($this->connectionMock);
+        $this->connectionMock->expects($this->once())
+            ->method('select')
+            ->willReturn($this->selectMock);
+
+        $this->model = (new ObjectManager($this))->getObject(Collection::class, [
+            'entityFactory' => $this->entityFactoryMock,
+            'logger' => $this->loggerMock,
+            'fetchStrategy' => $this->fetchStrategyMock,
+            'eventManager' => $this->eventManagerMock,
+            'mainTable' => null,
+            'eventPrefix' => 'test_event_prefix',
+            'eventObject' => 'test_event_object',
+            'resourceModel' => null,
+            'resource' => $this->resourceMock,
+        ]);
+    }
+
+    /**
+     * @covers \Magento\Customer\Model\ResourceModel\Group\Grid\Collection::setSearchCriteria
+     * @covers \Magento\Customer\Model\ResourceModel\Group\Grid\Collection::getAggregations
+     */
+    public function testSetGetAggregations()
+    {
+        $this->model->setAggregations($this->aggregationsMock);
+        $this->assertInstanceOf(AggregationInterface::class, $this->model->getAggregations());
+    }
+
+    /**
+     * @covers \Magento\Customer\Model\ResourceModel\Group\Grid\Collection::setSearchCriteria
+     */
+    public function testSetSearchCriteria()
+    {
+        $this->assertEquals($this->model, $this->model->setSearchCriteria());
+    }
+}